add constraints as comments

[gelpenaddict]

Some problems have constraints and it'd be helpful to mention it in the starter code as comments.

Example:
https://github.com/adnanaziz/EPIJudge/blob/master/epi_judge_python/convert_base.py

The function takes parameters num_as_string, b1, b2. The problem states that 2<=b1, b2<=16.
It'd be helpful to have those constraints as code comments.